The present invention relates to current controlling elements which are designed to function as multielectrode tubes such as tetrodes or pentodes used for radios, television sets, or the like.
Such a current controlling element or, a multielectrode tube has not only a plate and a cathode, but also a plurality of grids. For example, in the case of a tetrode, arranging a screen grid between a control grid and a plate reduces the electrostatic capacity therebetween to eliminate instability at high frequency occurring in the case of a triode, which prevents output characteristics from lowering due to a plate voltage drop occurring at the time of a high plate current.
Also, in the case of a pentode, arranging a suppressor grid between a screen grid and a plate further increases the screening effect to realize a stable operation, which provides a low distortion and large output.
Such a current controlling element controls a plate voltage to take out a current from the plate.
However, a conventional current controlling element requires an element like a power amplifier in order to control the plate voltage, which causes an increase of the cost. Also, using such an element provides a disadvantage of increasing the power consumption.
Besides, such an conventional current controlling element is difficult in integration. Therefore, it is not suitable for the current controlling element with a comparatively small size and a comparatively high current value.
It is therefore an object of the present invention to provide a current controlling element which is capable of reducing the cost and the power consumption.
It is another object of the present invention to provide a current controlling element which has a comparatively small size and a comparatively high power.
The present invention provides a current controlling element comprising an actuator having a fixed portion, a vibrating portion supported on the fixed portion so as to undergo vibrations, and an actuating portion including a first and a second electrode formed on both side surfaces or one side surface of a deformable layer, the actuator generating a displacement motion by holding an offset electric potential of the first electrode at a desired value and controlling variably an electric potential of the second electrode, a and a cathode formed on the actuator and emitting electrons. A plate for receiving the electrons emitted from the cathode and a grid arranged between the cathode and the plate are also proveded. The current controlling element changes the position of the cathode with respect to the plate by the displacement motion of the actuator obtained by changing an electric potential difference of the second electrode to the offset electric potential, and adjusting the offset position of the cathode according to the offset electric potential, to adjust a control range of a current value taken out of the plate.
According to the present invention, the current value taken out of the plate is controlled by changing the position of the cathode with respect to the plate by a displacement motion of the actuator, thereby enabling the electric potential of the plate with respect to the cathode to be held at a constant value, which eliminates the need of disposing an element, like a power amplifier, for controlling a plate voltage. This makes a current controlling element with a relatively low cost possible.
A control range of a current value taken out of the plate is adjusted by the offset electric potential, thereby providing the same function as a screen grid of a conventional multielectrode tube, which enables a screen grid to be omitted without impairing a function of the conventional multielectrode tube. This further lowers the cost.
Also, the voltage applied to the first and the second electrodes is less than the plate voltage. Therefore, changing only the voltage less than the plate voltage enables the plate current to be controlled, which results in a decrease of the electric power consumption.
According to an offset position of the cathode obtained by adjusting an offset electric potential of the first electrode, the control range of a current value taken out of the plate can be easily adjusted. For example, the insulating layer is formed on the first and/or the second electrode, and the cathode is formed on the insulating layer.
Preferably, the current controlling element comprises a plurality of cathodes corresponding to one plate, and a plurality of actuators corresponding to a plurality of cathodes, respectively. Thus integrating the actuators at a high density makes the current controlling element with a comparatively small size and a comparatively high current output possible.
Preferably, when constituting the actuator, the vibrating portion is formed of ceramics, the vibrating portion and the fixed portion are integrally formed, or the vibrating portion and the fixed portion are integrally formed of ceramics, or the actuating portion, the vibrating portion and the fixed portion are integrally formed. Further, the deformable layer is formed of at least one kind of a piezoelectric material, an electrostrictive material, and an antiferroelectric material.
Further, the current controlling device can be comprised of a plurality of the current controlling elements, and a substrate on which a plurality of the actuators of the current controlling elements are integrally formed. On this occasion, constituting a plurality of the current controlling elements as one element provides an electric control device which is capable of generating a comparatively high current, or a current controlling device having a plurality of current controlling elements separated by a cell construction and integrated together.
The present invention provides a current controlling element comprising an actuator having a fixed portion, a vibrating portion supported on the fixed portion so as to undergo vibrations, and an actuating portion including a first and a second electrodes formed on both sides or one side of a deformable layer, the actuator generating a displacement motion by holding an electric potential of the first electrode at a constant value and variable-controlling an electric potential of the second electrode, a cathode being formed on the actuator and emitting electrons and a plate receiving the electrons emitted from the cathode. The current controlling element changes the position of the cathode with respect to the plate by the displacement motion of the actuator to control a current value taken out of the plate, and the actuator maintains the displacement state by setting the electric potential of the first electrode at a certain value while holding the electric potential of the second electrode at the neighborhood of zero.
According to the present invention, as the actuator maintains the displacement state by setting the electric potential of the first electrode at a certain value while holding the electric potential of the second electrode at the neighborhood of zero, it is not necessary to apply the voltage continuously to the second electrode in order to maintain the displacement of the actuator. As a result, there is little power consumption resulting from the resistance of the current controlling element or a circuit including the current controlling element, and thus it is possible to reduce the power consumption of the current controlling element or the circuit including the current controlling circuit, because an actuator driving circuit is provided on the side of the second electrode and the power consumption resulting from the resistance of the actuator driving circuit can be omitted.
Preferably, the current controlling element further comprises a switching element which switches between the displacement motion and the maintenance of the displacement state of the actuator. Thereby, the switching between the displacement motion and the maintenance of displacement state of the actuator is well performed so that it is not necessary to apply the voltage to the second electrode in order to maintain the displacement of the actuator, and thus it is possible to reduce the power consumption of the current controlling element or the circuit including the current controlling circuit further more. Also, as there is no limitation of the choice of the actuator material to be subjected to the displacement motion and the maintenance of displacement state of the actuator, and thus the limitation of the choice of the actuator material is relaxed.
For example, the switching element has any one of transistor, a varistor and a piezoelectric relay. Especially, if the varistor is selected as the switching element, the limitation of choice of the actuator material is more relaxed because the good switching property can be obtained.
A current controlling element according to an embodiment of the present invention will be described with reference to the drawings.